Additional to its effects on vascular tone and platelet function, prostacyclin (PGI/2) is an important inflammatory mediator which modulates adhesive interactions and proliferative responses in vascular cells. Laminar, but not turbulent shear up-regulates cyclooxygenase (Cox)-2 in endothelial cells (ECs) in vitro. This project addresses the hypothesis that a deficiency of COX-2 dependent PGI/2 formation is of functional relevance to the relevance to the focal nature of atherogenesis. It relates to other projects in the program which examine the interaction of mechanical and humoral signaling pathways (Projects 1-4) and to the examination of the cell to cell heterogeneity in these interactions as outlined in Project 5. We shall utilize the LDLR edit mouse deficient in both the LDL receptor and the ability to edit apoB, as our preliminary model of atherosclerosis. Lesions are developed on a chow diet, are more severe than in traditional models and evolve in a distribution which resembles human atherogenesis. Additionally, their elevated cholesterol resides predominantly in LDL. In Specific Aim 1, we shall utilize both specific COX-2 inhibitors and the COX-2 knock out (KO) mouse to determine the functional importance of products of products of this enzyme in the extent of atherosclerosis, the response to vascular injury, platelet function and thrombosis and aspects of cardiovascular function in atherosclerotic mice. In Specific Aim 2, we shall utilize a similar strategy of comparative analysis of selective inhibitors and gene deletion to address the role of COX-1, the isoform which is usually expressed constitutively in the vasculature. In Specific Aim 3, inhibitors are not available to address the role of PGI/2. However, we have generated receptor (IP) KO to asses the influence of the major COX- 2 product in vascular cells. If the effects of IP deletion differ markedly from our COX studies, we shall explore the relevance of other COX products, such as E prostaglandins, particularly if supported by results of PG profiling analysis, using mass spectrometry. In Specific Aim 4, we shall utilize structurally distinct COX-2 inhibitors to assess the role of this isozyme in the disordered platelet and endothelial function in patients with peripheral vascular disease. Comparative experiments with a platelet selective form of aspirin and a thromboxane receptor antagonist will allow us to investigate the role of TxA2. Integration of these studies of murine and human cardiovascular function will allow us determine if a localized deficiency in shear induced COX-2 production of PGI/2 is of functional relevance to atherosclerosis. As selective COX-2 inhibitors depress biosynthesis of PGI2 without concomitant inhibition of platelet function, this is an issue of clinical importance.